Recently during a storm, I lost power to my whole house. For ~30-60 seconds after losing power, 3-4 CFL bulbs continued to glow faintly. The bulbs were on different circuits, and legs of the 120/240V residential electrical system. One of the bulbs was even part of a multi-bulb fixture, where the other bulbs in the fixture all turned off.

I suspected possible backfeeding. But I wouldn't expect single bulbs in multiple bulb fixtures to get power while the others did not, if this was caused by backfeeding.

What could have caused these bulbs to continue to glow after power was lost?

1 Answer
1

This is normal for fluorescent bulbs. You should be able to see the same thing when you turn off the light fixture using a regular switch instead of dropping a tree across your power line.

Fluorescent lights generate light by an electrical discharge through the mercury vapor in the tube; the mercury emits UV light, which excites electrons in the phosphorus coating the tube. When those electrons decay, they emit visible light. However, there can be a delay between excitation and decay, so you'll see some light emitted for a while after the bulbs lose power.

Variations in construction between manufacturers or even between individual bulbs mean that they'll glow for different amounts of time.

@Tester101 I don't think glowing for 1 minute would be unusual. Did the rest of your neighborhood lose power as well? If so, the glow would be even more noticeable than if you just turned off the power since there'd be no ambient light sneaking in past the edges of your curtains or whatever. There's also the effect where you can use static electricity to make a fluorescent tube glow so there might be some backfeeding going on.
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Niall C.♦Nov 19 '12 at 20:42